Fracture toughness of Al2O3-Ni composites with nickel aluminate spinel phase NiAl2O4
Katarzyna Konopka, Aleksandra Miazga, Jolanta Właszczuk
Quarterly No. 3, 2011 pages 197-201
DOI:
keywords: cermetals, Al2O3, fracture toughness, spinel phase
abstract The article presents the results of research on the modification of the properties of ceramic Al2O3 using particles of nickel. As starting materials, powders of Al2O3 and Ni were used, from which mixtures of Al2O3+x% vol. Ni (x = 0, 1, 3, 5) were prepared. They were subjected to sintering in an argon atmosphere at 1450°C for one hour. The physical properties of the composites such as: density, porosity, absorptivity and contractility were determined. Moreover, analyses of the received phase composites (from the surface and cross-section) have been made using the diffraction method, which showed NiAl2O4 spinel phase formation. Spinel is formed mainly at the border of Ni and Al2O3 grains. It was confirmed in the microstructure photographs taken using scanning and transmission electron microscopy methods. The mechanical properties have been investigated:hardness HV, nanohardness and fracture toughness (crack length measurement method with Vickers indentation). As the amount of nickel hardness HV decreased from 17.3 GPa to 100% Al2O3 to 13.2 GPa for Al2O3 + 5%vol. Ni, the nanohadrness values increased, which could have been caused by the presence of a spinel phase. The composites were characterized by higher resistance to brittle fracture than 100% Al2O3. This was due to blocking, deflecting and bridging cracks in nickel and by branching cracks by spinel particles.